Custom Color Screen Test: Fullscreen Check for Any Monitor
Custom Color Screen Test. Click Start Custom Color Test and pick any Test color to run a fullscreen color screen test on your monitor. The free white screen test runs fullscreen so you can inspect your panel edge-to-edge under real viewing conditions.
Interactive Tool
This color is the first pattern when you click Start. The picker in the fullscreen controls bar changes it too.
Custom Colour Fullscreen is a color screen test that lets you pick any color you like and push it across your entire display, instead of being limited to the standard red, green, blue, black, and white test set. Enter fullscreen, open the color picker in the on-screen controls, and choose the exact color you need for a dead-pixel check, a plain presentation backdrop, or a quick color-match reference.
Want to know exactly what your screen does with one specific shade? The custom color fullscreen screen test is a color screen test that fills every pixel of your display with any shade you choose, so dead pixels, tint and uneven backlighting have nowhere to hide. It is free, needs no download, and runs the same test patterns factory QC benches use, so you get a fast read on color accuracy and display defects on a monitor, laptop, phone or TV.
How the Custom Color Fullscreen Screen Test Works
Pick a shade, then click the preview or press F to switch to fullscreen mode. The whole screen then shows one flat field at your native resolution. Use the arrow keys to step through preset colors and Esc to leave full screen. The test runs in the device's own browser, and any modern web browser works on a smartphone, tablet or laptop, with no registration. Nothing is uploaded, so privacy is a non-issue, and the page keeps working offline once loaded. The info strip also reports the device resolution and DPR, which confirms the field covers every physical dot on your devices.
Picking a Custom Color with the Color Picker
The color picker accepts a hex code such as #FFFFFF or any value you type. The three hex pairs are the RGB color channels, each converted with a simple rule:
$$\text{channel value} = 16 \times d_1 + d_2$$
Take a brand teal of #1F8A8C. 1F gives \(16 \times 1 + 15 = 31\), 8A gives \(16 \times 8 + 10 = 138\) and 8C gives 140, so the display is asked for R 31, G 138, B 140. Filling the display with that one solid color turns it into a color screen for checking how your own brand shade actually renders, something preset colors can't show.
What Each Solid Color Reveals on a Monitor Test
A full monitor test works because every flaw stands out against a flat field of the right shade. Cycling full-screen solid colors, the primary colors plus black, white and gray, is the core test pattern for finding display defects on any panel. Use the free stuck pixel fixer online to confirm everything looks correct before you rely on it elsewhere.
| Background | Best at revealing | What a fault looks like |
|---|---|---|
| Black | Backlight bleed, bright dead pixel faults, contrast | Glowing corners or lit dots |
| White | Dark spots, dust, tint | Black specks or a color cast |
| Red, green, blue | Missing subpixels | A dark dead pixel on one channel only |
| Neutral gray | Uniformity, color temperature drift | Patchy or tinted areas |
| Gradient | Banding | Visible stripes instead of a smooth ramp |
| Gray boxes, angled view | Color-shift on TN and VA panels | Boxes that change shade with viewing angle |
Black Screen Test for Backlight Bleed and Clouding
Dim the room first, since ambient light hides faint glow. On a black screen test, a black screen should look uniform. Light leakage at the edges is backlight bleed (also called screen bleeding), and blotchy patches in the middle are clouding. OLED shows true blacks, so any bright spots there point to a pixel fault, not the backlight.
White Screen for Dust, Tint and Dark Spots
Wipe the glass with a microfiber cloth first; a lot of "dead pixels" turn out to be dust. A white screen then shows dark spots and tint. White should look neutral, close to the D65 standard, with no pink or green color cast across one side.
Red, Green and Blue Dead Pixel Test
Each pixel is built from red, green and blue subpixels. In a dead pixel test, a dot that stays dark on all three is a dead pixel; a dot dark on only one channel means a single failed subpixel. A 2560 × 1440 monitor has 3,686,400 pixels and 11,059,200 subpixels, so scan in a grid rather than at random.
Gray Fields for Screen Uniformity and DSE
Step through grayscale steps at different brightness levels to judge screen uniformity. Darker corners are vignetting, and cloudy smudges on a mid gray are the dirty screen effect (DSE), most visible when the camera pans in dim scenes. On an OLED display, add a 5% gray: OLED pixels switch fully off at black, so near-black blotches show up here that a pure black field hides.
Checking a Used OLED Laptop with a Magenta Color Test
The decision on the table: buy a two-year-old 14-inch OLED laptop at 2880 × 1800 for $642, or walk away. The seller has it open on a café table, so I have about five minutes and no colorimeter. The short answer came fast: one stuck green subpixel, well inside the ISO pixel-fault allowance, and no burn-in. The red screen test is free and runs entirely client-side, so nothing about your display is ever uploaded.
I open the screen test in the laptop's own browser, check that the info strip reads 2880 × 1800 at the native setting, and press F. White and black come first and look clean. Red and blue are clean too. On the green field nothing shows, which is exactly the trap: a subpixel stuck on in green is invisible on green and barely visible on white.
So I type a custom color, #FF00FF. Magenta drives red and blue at 255 and green at 0, so any green subpixel that is stuck lit turns its pixel pale against the field. One appears about 66% across and 36% down, near pixel 1,912 × 644. That is the result the custom color fullscreen test exists for: a fault that preset colors hid.
Next I check it against a published bar. ISO 13406-2 Class II, the allowance most laptop makers still quote, permits 5 subpixel faults per million pixels. This panel has 5,184,000 pixels, so:
| Panel | Pixels | Subpixel faults allowed (Class II) |
|---|---|---|
| 2880 × 1800 (this laptop) | 5,184,000 | 25 |
| 1920 × 1200 (same size, lower spec) | 2,304,000 | 11 |
I recompute 5.184 × 5 by hand to be sure: 25.9, rounded down to 25. One fault is far inside that, though the allowance would not get me a warranty swap either.
The last check is burn-in. I enter #2E2E2E, an 18% gray, and look for a taskbar ghost. None.
The number to watch here is not the fault count but where it sits: 66% across is inside the area a spreadsheet's white cells cover all day, where a lit green dot would show. My call is to offer $595 and point at the dot. The caveat: a stuck subpixel can come back to life or a second one can appear, and a five-minute café check can't predict which, so I keep the seller's 14-day return option in the deal.
Color Accuracy Test Patterns: Gradients, Shift and Distance
A color test goes past defects to color reproduction. Photography, videography, photo editing and graphic design all depend on skin tones and brand color patches looking right, which is where calibration and color calibration checks come in.
Gradients and Color Banding on 8-Bit Panels
A smooth gradient should blend without steps. An 8-bit panel can quantize a ramp into visible stripes, which is color banding. Check grayscale ramps for even color temperature, then the red, green and blue gradients and color bars; banding on only one channel points to a processing or cable issue.
Color-Shift and Viewing Angle on IPS and TN Panels
TN and VA screens change shade as your viewing angle moves, a color-shift that also lowers contrast. Sit square to the screen, match six gray boxes, then look from each side. On IPS or older S-IPS panels the boxes should hold steady.
Delta E: Measuring Color Difference Between Two Swatches
Color distance is scored as Delta E (ΔE), the color difference between two swatches in the CIELAB space:
$$\Delta E = \sqrt{(L_2 - L_1)^2 + (a_2 - a_1)^2 + (b_2 - b_1)^2}$$
Our teal #1F8A8C converts to L 52.24, a −27.69, b −9.49. If your monitor renders it like #23888F (L 51.78, a −25.27, b −11.93), the result is ΔE ≈ 3.46. Below 1 is invisible; 2 to 10 is visible at a glance, so this shift is one you'd notice side by side. With this tool, put your hex on screen beside a printed brand swatch: a mismatch you can see means roughly 2 or more, and the exact figure needs a colorimeter.
When to Run a Free Online Screentest on OLED and LCD
A free online screen test is worth running on any OLED, AMOLED or LCD display, and a screen test online works the same on a television browser. Run the online screen test once at purchase, after a GPU driver or cable change, and as a monthly quick look.
New or Used Monitor, Laptop and Phone Checks
The first week is the critical window: defect rates peak in new screens and the return window is short, so photograph faults for a warranty claim or exchange. On a used monitor or phone, a two-minute sweep belongs in every pre-purchase inspection. On an OLED phone, run it on the device itself at full brightness.
OLED Burn-In and Image Retention Checks
Static logos can cause burn-in, mostly an OLED concern because each OLED subpixel dims with use. Show a mid gray field and look for ghost outlines of taskbars or channel logos. Faint shapes that fade within minutes are image retention; a screen saver and lower brightness help prevent both on OLED.
Dead Pixel or Defect? Reading Your Fullscreen Results
Note where each fault appears and on which background. Use a fullscreen test on several colors before you label anything, since one full-screen test background can mislead.
Stuck Pixels vs Dead Pixels vs Hot Pixels
- Dead pixels stay black on every color and are usually permanent.
- Stuck pixels stay lit in one color; a stuck pixel can sometimes recover with rapid flashing.
- Hot pixels stay bright white on a black field.
Ghosting, Refresh Rate and Hardware Calibration Limits
Static colors can't show ghosting, motion blur or response time, so pair them with a moving test and confirm the refresh rate; OLED switches almost instantly, so smear there usually points to processing on the display side. Measured gamma and exact color error need hardware calibration with a colorimeter.
Frequently Asked Questions
- What is a custom color screen test?
- It fills your entire display with one color you choose, by hex code or RGB values, so any pixel or area that behaves differently stands out. Preset black, white, red, green and blue cover the classic checks, and a custom color lets you test the exact shade you care about.
- How do I run a fullscreen color test?
- Pick a test color or enter a custom hex, then press F or click the preview to enter fullscreen. Use the arrow keys to step through colors and press Esc to exit. Clean the screen and dim the room first.
- Which color shows dead pixels best?
- Use several. A dead pixel shows as a dark dot on white, red, green and blue; a stuck or hot pixel shows as a bright dot on black. A stuck green subpixel is easiest to see on magenta (#FF00FF), where green is switched off.
- Can I test a phone, laptop or TV with this?
- Yes. Open the page in the device's own browser, including a smart TV browser, and enter fullscreen. Phones and laptops benefit from the full solid-color sweep; TVs from the black and gray uniformity checks.
- What does the Delta E result mean?
- Delta E is the CIELAB distance between your test color and the Compare With color. Under 1 the two look identical, 1 to 2 is visible only on close inspection, 2 to 10 is visible at a glance, and above 10 they read as different colors.
- Is the screen test free and private?
- Yes. It is free, needs no download or account, and every color is generated in your browser, so nothing about your display is uploaded.
- How often should I test my monitor?
- Thoroughly when you buy it, inside the return window, again after a GPU driver or cable change, and with a quick gray-field check about once a month on OLED screens to catch burn-in early.